Stephanie J. Sheehan
Students will conduct a series of sorting lessons that will help them to observe various properties of solids. After each experience, the students will create a journal entry describing what they were looking for, what they observed, and anything interesting they noticed. They will also have to create labeled drawings to show what they did with the materials they observed. A sample log page can be found in Appendix 3.
For the first activities with solids, students will sort all twenty objects, such as a clear plastic cube, a red, wooden golf tee, and a metal ball by color and then by shape. Of course, they will record their observations with pictures and labels in their science journals.
After sorting by these familiar attributes, the students will examine the objects to see whether they roll or stack. They will use a Venn diagram to keep track of their findings
13
. For this activity, the teacher will draw the two interconnected circles to make a large Venn Diagram on a sheet of paper at least 36" by 20" with the left circle labeled "rolls," the right circle labeled "stacks," and the middle overlapping area labeled "both". Then, he or she will instruct the children to test the objects and place them on the Venn diagram in the appropriate spot. (Objects that neither stack nor roll should be placed on the paper outside the Venn diagram.) The children will discover what each solid object does and write and draw their findings in their science journals. Then, the teacher should display the shampoo, water, corn syrup and oil. Students should be given droppers to test drops of the liquids for their ability to stack or roll. The students will discuss why the liquids are not able to stack or roll and write their observations in their journals before cleaning up.
For the next activity the students must arrange the objects in a continuum according to their hardness, from the softest item to the hardest
14
. The students will learn that it is often important to describe objects in comparison to others in order to be specific. They will realize that solids can be hard or soft and yet retain or regain their shape after the pressure is removed. They will describe the objects as specifically as they can and distinguish a soft solid from a liquid. At this time, it might be helpful to demonstrate the difference between a soft solid and a liquid, using a sponge ball and a water balloon. The teacher will gently toss the water balloon and sponge ball in the air and allow students to squeeze and examine each. Then, he or she will drop both items on the floor, which will cause the water balloon to break and the water to spill all over the floor. The students will notice that the sponge ball retained its original shape after being dropped while the water, which had taken the shape of its water balloon "container" has now taken the shape of the floor
15
.
Expanding Knowledge of Solids with Food
To expand their experiential learning and further excite the students about learning the properties of solids, the teacher will revisit the previous activities using objects from the kitchen. First, he or she will display the following familiar items: cold butter, rice, pickles, carrots, sweet potatoes, hard candies, chocolate bars, ice cubes, hard boiled eggs, vinegar, pancake syrup, orange juice, milk, soda, sugar, salt, frosting, mayonnaise, egg yolks, and uncooked bread dough. The students will have to examine each item and identify which of the items are solids. The children will do this by listing the names/pictures of the items on a three- column chart labeled solid, liquid, and unknown. Based on the definition that a solid has a definite shape of its own, and the sorting and observing they have done so far, the students are likely to choose the first nine items. Perhaps they may decide to include the salt and sugar as well. If no one does, the teacher might challenge the students to consider whether they should be sorted according to one grain or the whole amount as one item. If it doesn't happen automatically, the teacher will also encourage the class to consider whether the frosting, dough and mayonnaise should be considered solids. They will discuss the circumstances under which they act like solids or act like liquids.
After experimenting with several of the foods, they may realize that a substance might be considered a solid or a liquid depending on how long you let it sit or how hard you push on it. For example, the bread dough does not immediately flow and fill up the container it is in, but it will eventually spread out over time. Similarly, if you push the frosting or dough into a certain shape, it would not resist and go back to its original shape like a sponge or a rubber ball would. They will continue discussing and debating as necessary until an agreement is achieved among the class members. After the students have come to an agreement, then they will examine and sort them according to their color, shape and whether they roll or stack.
After the science teams have had a chance to sort by the various properties and arrange their solids according to hardness, they will share with the class and discuss any differences among the answers that were found. The teacher will create a chart showing the final results of each activity for the class to view and refer to. Of course, the students will also draw and write about each of these experiences in their science journals. Please note that the students should be advised not to consume any of the science materials unless they are given explicit permission to do so. Students will utilize disposable trays and newspaper to contain any mess that may be produced by these activities.
Next, the students will experiment with all of the original household objects and the additional kitchen materials in whatever way they would like to for ten minutes. Then, they will play sorting games in which one partner sorts by a mystery rule and the other must guess the rule
16
. The students will continue to keep journal entries describing each of these experiences.
Then it will be time to challenge some of the assumptions the students have. The students will already be noticing and commenting that the ice cubes have started to melt by the end of the sorting activities and therefore are changing into liquid water. The teacher should encourage the students to consider what might cause some of the other materials to change their state as well. He or she should also encourage the class to discuss their experiences with food and to share their background knowledge, such as watching melting butter on a warm day or seeing it melt in a pan as part of a recipe.
The students will now look closely at the rice, salt, and sugar. They will use magnifying lenses to identify the small grains of salt and sugar and discuss how these substances would be categorized according to their shape, color, rolling vs. stacking ability and hardness. Then, they will pour the substances into containers of various shapes and see that they do take on the shape of the container they are in when observed as a group. However, each grain of salt, sugar or rice has its own definite shape. In this case, it depends how closely you look at the substances and the individual particles that they are made up of.
Examining Liquids
The students will now examine and compare liquids. They will begin by comparing water, shampoo, and glue. They will stir, tilt, feel and look at them closely. They will compare the way they drip and pour as well as the color, feel and thickness. Then, they will investigate to see how quickly or slowly they flow. They will learn the term viscosity. They will use zip-lock bags to see the fluidity and to see how liquid can take on the shape of the container it is in. The students will perform drop races to see how quickly or slowly the liquids flow
17
. The students will be instructed to attempt to form the liquids into a definite shape and write in their journals about what they observed.
Students will then choose the substances from the kitchen materials I have on display that they think are liquids. The students will undoubtedly choose the syrup, soda, vinegar, orange juice, and milk. Encourage debate and discussion to decide if the sugar, rice, mayonnaise, frosting, and dough should be included as well. After the liquids have been chosen and distributed, students will observe them by touching, stirring, and tilting them. They will then examine them by moving them inside zip-lock bags and conducting drop races. In addition to writing about them in their journals, they will arrange and order all the liquids in several ways to show their observations. They will preserve their observations by drawing them on paper strips. First, the students will sort the liquids by color and arrange them from darkest to lightest. Then, they will arrange them from least viscous to most viscous. Finally, they will arrange them by clarity, from the most opaque, which will not allow light to pass through (glue), to the most translucent, which will allow light to pass through (water). In the latter case, it is possible to look through the substance.
For a fun extension, students will make "magic mud," (which is often called "oobleck") by combining 5 tablespoons cornstarch with 3 tablespoons water and a few drops of food coloring in a mug
18
. The "magic mud" feels solid when strong pressure is applied quickly, but when less pressure is applied, or applied slowly, the "mud" becomes liquid and is able to flow.
19
The students must examine it by pouring, touching, and spreading it inside a zip-lock bag and on a paper plate. The students will have to decide where the magic mud should be placed on the continuums they have created for the liquids they have already arranged. (They will also have to be able to explain why.)
